Inkjet recording methods enable simple and inexpensive image production and have therefore been used for printing of, for example, paints, adhesives, printing inks, circuit board materials, and electrical insulating materials on plastics, paper, woodwork, inorganic materials and other materials. As the inkjet recording method, UV-curable inkjet method is known wherein droplets of ink are landed on a recording medium and then cured by irradiation with ultraviolet rays to form an image. Recently, the UV-curable inkjet method has been attracting attention for its capability of forming images having high rubfastness and adhesiveness even on recording media which lack ink absorbing properties.
As UV-curable inkjet inks having high pinning properties, for example, inks have been proposed which contain a gelling agent and undergo temperature-induced sol-gel phase transition (see, e.g., PTL 1). Specifically, ink droplets that are in liquid state at high temperatures are discharged and landed on a recording medium, and at the same time are cooled for gelation on the recording medium, whereby combining of dots can be prevented.
On the other hand, as a light source for irradiating gelling agent-free UV-curable inks or radically polymerizable curable wax-containing UV-curable inks with ultraviolet rays, ultraviolet ray-emitting diodes (UV-LEDs) have been proposed (see e.g., PTLs 2 and 3).